On Saturday night Rudy Giuliani, the former mayor of New York who has become one of Mr Trump’s closest advisers, announced that he no longer believed in the two-state solution.

"You can make peace between the two of them, but you can't treat them the same," he said, condemning moral equivalence between the two parties. The US, he said, should "reject the whole notion of a two-state solution in Israel."

Mr Trump's two top advisers on Israel issues, Jason Greenblatt and David Friedman, have also advised the candidate to abandon hopes of two states for two peoples living peacefully side by side, according to the Jerusalem Post.

Mr Trump also appears to have discussed his much-vaunted wall between Mexico and the US, with the campaign stating that they “discussed at length Israel’s successful experience with a security fence that helped secure its border.”

Mrs Clinton also met with Mr Netanyahu – whom she has known for many years. The Democratic nominee talked with Mr Netanyahu during a closed-door meeting at the W Hotel in Union Square, New York.

Her campaign said the two had an "in-depth conversation." She stressed "a strong and secure Israel is vital to the United States" and "reaffirmed unwavering commitment" to the relationship.

According to her campaign, Mrs Clinton stressed her support for the 10-year, $38 billion military aid package signed between the two countries earlier the month and opposition to efforts to boycott Israel. They also discussed Iran, the conflict in Syria and other regional challenges.

Unlike Mr Trump, Mrs Clinton discussed her support for a two-state solution to the Israel-Palestinian conflict negotiated by the two parties - not an outside organisation like the UN Security Council.

The Democrat nominee has assiduously courted Jewish voters, with her campaign website making much of her three-decade public commitment to Israel, dedicating an entire page to her personal, diplomatic and legislative history with the country under the headline: “Hillary Clinton and Israel: A 30-Year Record of Friendship, Leadership and Strength.”

The meetings will doubtless be more ammunition for both candidates in Monday's presidential debate.

Billed as “the Super Bowl of debates” - with 100 million viewers expected to tune in - a poll was released on Sunday showing a virtual dead heat in the race for the White House.

The Washington Post-ABC News poll showed Mrs Clinton and Mr Trump tied among registered voters at 41 per cent, with Libertarian candidate Gary Johnson at 7 per cent and Jill Stein, of the Green Party, at 2 per cent.

And viewers were eager to see whether Mrs Clinton would indeed come face to face with her husband’s former mistress, after Mr Trump speculated that he could invite Gennifer Flowers to the presidential debate.

In a sign of how dirty the election campaign has become, Mrs Clinton has reportedly invited a nemesis of Mr Trump’s, businessman Mark Cuban, owner of the Dallas Mavericks basketball team, to attend the debate.

The two billionaires, who have both been reality show stars and larger-than-life personas, have feuded regularly in recent years.

On Saturday Ms Flowers told the New York Times that she would attend the debate, at New York’s Hofstra University, texting a reporter at the paper to say: "Yes, I will be there."

Ms Flowers said during Bill Clinton's 1992 presidential campaign that the two of them had engaged in a lengthy affair over a dozen years. The allegation, which Mr Clinton denied at the time, threatened to ruin his campaign – he finally admitted the affair in 1998.

But on Sunday Mr Trump’s team were quickly backpedalling, saying that Mr Trump was just attempting to show that he could “counterpunch” if need be.

“Donald was using the tweet yesterday really to mock an effort by Hillary Clinton and her campaign to really distract attention from where the people — the American people — are going to be focused tomorrow night, which is on the issues. It’s on the choice that we face.”